fiber.hh

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/*
 * Copyright 2018 Google, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
#ifndef __BASE_FIBER_HH__
#define __BASE_FIBER_HH__
 
// ucontext functions (like getcontext, setcontext etc) have been marked
// as deprecated and are hence hidden in latest macOS releases.
// By defining _XOPEN_SOURCE we make them available at compilation time.
#if defined(__APPLE__) && defined(__MACH__)
#define _XOPEN_SOURCE 600
#include <ucontext.h>
#undef _XOPEN_SOURCE
#else
#include <ucontext.h>
#endif
 
// Avoid fortify source for longjmp to work between ucontext stacks.
#pragma push_macro("__USE_FORTIFY_LEVEL")
#undef __USE_FORTIFY_LEVEL
#include <setjmp.h>
#pragma pop_macro("__USE_FORTIFY_LEVEL")
 
#include <cstddef>
#include <cstdint>
 
#include "config/have_valgrind.hh"
 
class Fiber
{
  public:
    const static size_t DefaultStackSize = 0x50000;
 
    Fiber(size_t stack_size=DefaultStackSize);
    Fiber(Fiber *link, size_t stack_size=DefaultStackSize); // end of api_fiber
 
    virtual ~Fiber();
 
    void run();
 
    bool finished() const { return _finished; };
 
    bool started() const { return _started; };
 
    static Fiber *currentFiber();
 
    static Fiber *primaryFiber();
 
  protected:
    virtual void main() = 0;
 
    void setStarted() { _started = true; }
 
  private:
    static void entryTrampoline();
    void start();
 
    ucontext_t ctx;
    // ucontext is slow in swapcontext. Here we use _setjmp/_longjmp to avoid
    // the additional signals for speed up.
    jmp_buf jmp;
 
    Fiber *link;
 
    // The stack for this context, or a nullptr if allocated elsewhere.
    void *stack;
    size_t stackSize;
    void *guardPage;
    size_t guardPageSize;
#if HAVE_VALGRIND
    unsigned valgrindStackId;
#endif
 
    bool _started;
    bool _finished;
    void createContext();
};
 
#endif // __BASE_FIBER_HH__